Wk 4: nervous system Flashcards
Central Nervous System (CNS)
brain AND spinal cord
Peripheral Nervous System (PNS)
nerves and autonomic ganglia (part of the ANS)
Communication lines between the CNS and the rest of the body
PNS relays information from:
Internal: viscera, afferent nerves (IV)
External: sensory, afferent nerves
Sent to CNS and includes efferent responses from brain to target cells/organs (efferent).
Parasympathetic
“rest and digest”
conserves energy
Sympathetic:
“fight or flight”
mobilises body systems during activity
Somatic:
Skeletal
Types of cells in CNS
Neurons and Neuroglia
Neuroglia
specialized cells found in close association with neurons
(Don’t participate directly in information transfer)
Neurons
excitable cells that transmit a nervous message
Types of neuron cells
- Multipolar neuron (motor neuron & interneuron): most common
- Bipolar neuron (sensory neuron, eye and ear): rare
- Pseudo unipolar (sensory neuron): frequent in this neuron
Four types of glia
Oligodendrocytes
Astrocytes
Microglia
Ependymal
Oligodendrocytes
makes myelin on axons
1oligodendrocyte : 60 axons
Astrocytes
Roles
- Structural support
- Provides nutrients/homeostasis for neurons
- Maintains/regulates synaptic connections
- Reacts to injuries = astrogliosis
Microglia
resident macrophages in the brain “the brains immune cells”
increase in phagocytosis after injury results from migration of cells to the injured area
Ependymal cells
provide lining in the ventricles and help produce Cerebro-spinal Fluid (CSF)
Types of glial cells in PNS
Schwann cells
Satellite cells
Schwann cells
divide frequently, myelinate fast and are highly resistant to injury
(Similar function to oligodendrocyte)
Satellite cells
support neurons and enhance their function
(Similar function than astrocytes)
RMP
the electrical potential difference across the plasma membrane when the cell is in a non-excited state
RMP depends on
- Permeability
- Electrochemical gradients
- Presence of Na+/K+ on the neuronal membrane
Methods of propagating action potentials
- Continuous propagation (in unmyelinated axons)
- Saltatory propagation (in myelinated neurons)
Synapses
junctions between neuron/cell allowing them to communicate with one another
Types of synapses
1) Electrical: gap junction (bidirectional): very fast connection present mainly in brain and heart
2) Chemical: (unidirectional) most common ones in mammals.
Neurotransmitters
released at presynaptic membrane (exocytosis) and bind to specific receptors at the postsynaptic neuronal membrane
Mechanisms to inactive neurotransmitters in the synaptic cleft
- Broken down by specific enzymes in synaptic cleft
- Reuptake at pre-synaptic button by specific transporter
- Diffuse away
Neurotransmitters in the brain
- Glutamate
- GABA (Gamma-aminobutyric acid)
Glutamate
excitatory neurotransmitter in CNS
Function: learning and memory
Acts on metabotropic and ionotropic receptors
GABA
inhibitory neurotransmitter in CNS
Act on GABAergic receptors which are a ligand gated channel receptors
Ligands of the receptors
GABA
ethanol
benzodiazepine
barbiturate
Other neurotransmitters
Catecholamines:
* Noradrenaline
* Serotonin
* Dopamine
Acetylcholine
Peptides
* Endorphins
Noradrenaline
concentration, energy, anxiety
Serotonin
memory, mood, obsessions, compulsions, appetite
Dopamine
reward, pleasure, motor control
Acetylcholine
motor activity and memory
Endorphins
act as natural pain and stress relievers
Brain anatomy and function includes
Dura Mater
Arachnoid Mater
Pia mater
Dura Mater
external layer which is thick, tough, inelastic
Arachnoid Mater
thin cell layer with arachnoid trabeculae, which is web-like collagen projections to pia layer.
subarachnoid space containing CSF
Pia mater
internal layer; thin, delicate, tightly that covers all external contours of brain with blood vessels.
Structural components of the brain
Thalamus
Midbrain
Hypothalamus
Thalamus
relay and processing centers
Hypothalamus
- Highest centre for autonomic control
- Control and integration centre connected to the limbic system (emotion, behaviour, memory)
- Appetite regulation
- Hormonal regulation
Midbrain
region of motor control, sleep/wake, arousal, and temperature regulation
- Relay station for auditory and visual information
Pons
contains subconscious somatic and visceral centres
- Relays sensory info to cerebellum and thalamus
Medula Oblongata
Contains autonomic centres for regulation of** visceral function
**
Cardiovascular, respiratory and digestive activities
- Relays information
Brain stem
formed from midbrain, pons and medulla oblongata
- Gives rise to the majority of cranial nerves
Corpus Callosum
connects the two hemispheres
- Mainly made of mainly nerve fibres
- Function: role for lateralisation
Cerebro Spinal fluid (CSF) located in
- 2 lateral ventricles (1 in each cerebral hemisphere),
- Third ventricle in the diencephalon
- Fourth ventricle in the Brainstem
Cerebro Spinal fluid functions
- Cushions delicate neural structures
- Supports brain
- Transports chemical messengers, and waste products
Blockage in the blood vessels can cause
stroke
Ischemic stroke
there is ablocked or closed vessel
Haemorrhagic stroke
there is a rupture in the blood vessels and cause bleeding
Cerebral cortex made of
- Blanket of cells covering the cerebral hemispheres
- Grey matter
- Neurons, axons, dendrites
How is the cerebral cortex organised
Primary (simple levels of processing)
Associative cortical areas (integrate and process information from relevant senses)
Lobes forming cerebral cortex
Frontal lobe
Parietal lobe
Occipital lobe
Temporal lobe
Frontal lobe
includes primary motor cortex
- Function: motor control and language production
Parietal lobe
includes somatosensory cortex
- Function: perception of touch, pressure, pain, vibration, taste
Occipital lobe
include visual cortex
- Function: vision
Temporal lobe
with auditory and olfactory cortices
- Function: audition, olfaction and language comprehension
BASAL GANGLION function
motor planning
executing fine voluntary
CEREBELLUM function
Allows rapid co-ordination for movement, automatic adjustments to maintain balance and posture
